Question: Nadia had to do problems 28 through 47 for homework tonight. If Nadia did all of the problems she was assigned, how many problems did she do?
Answer: Instead of counting problems 28 through 47, we can subtract 27 from each number so we instead consider problems 1 through 20. We see that Nadia did 20 problems. Notice that she did 20 and not 19 problems.